The present invention relates to a recorded-information reproducing apparatus. More particularly, the invention relates to a recorded-information reproducing apparatus for reproducing a recording medium on which is recorded a video FM signal and a digital audio signal frequency-division multiplex recorded thereon.
As recording media carrying video FM signals and digital audio signals frequency-division multiplex recorded thereon, so-called Hi-Fi video disks on which well-known video disk recording signals and EFM (eight-to-fourteen modulation) digital audio signals in a CD (compact disk) format are multiplex recorded have been commercialized. In such a Hi-Fi video disk, analog audio FM signals for two (right and left) channels are included in the information recorded on the disk. In the case, however, where the video signal band, determined by the width of the sidebands of the video FM signal, is made too wide, both the reproduced video and analog audio signals are affected by interference with the analog audio carrier. Consequently, it is difficult to make the video signal bandwidth more than about 4.2 MHz, resulting in a limit in resolution.
In this regard, in commonly assigned Japanese Patent Application No. 61-305782 there has been proposed a recording system in which no analog audio FM signal is recorded, and only an EFM digital audio signal is recorded as the audio signal so as to widen the available video bandwidth to thereby improve the resolution. FIG. 1 shows the frequency spectrum of a high frequency signal read from a recording medium carrying information recorded with the foregoing recording system. In the drawings, A.sub.- represents an EFM digital audio signal, and A.sub.+ represents the upper sideband generated as a result of pulse-width modulation multiplexing Y represents the spectrum of the video FM signal, and C.sub.+1 and C.sub.-1 respectively represent the upper and lower first sidebands of the chroma signal contained in the video signal. Further, I.sub.1 and I.sub.2 represent main components of an interference spectrum generated as a result of pulse-width modulation multiplexing of Y and A.sub.-.
FIG. 2 shows the frequency spectrum of a video signal output obtained by demodulating a high frequency signal having a frequency spectrum as described above and which is read from a recording medium. As seen from the frequency spectrum, a high-level interference component due to I.sub.1 is present in the video signal band at the high frequency end. This high-level interference component may cause beat interference in the chroma component C, lowering of the SN ratio of the Y (luminance) signal, or deterioration in the quality of the reproduced picture.